Nice! Looks like your gonna use the push fit cartrages
The radius on the stepped hole isnt needed, itll probably speed up the process a little bit.
I too am designing some with those cartrages, I dont really like how thick the top needs to be, but It can be worth it
Cant see from here, but did you mill the mounting slots before milling around the peice? I would suggest that because youll have a heck of a time trying to mount that thing back in a vice or whatever.
Ya also want to make sure you dont chop into the vice
-edit- what kind of machine are you making it on and out of what material?
Jon